Re-crosslinking particle gel for CO2 conformance control and CO2 leakage blocking

RELATED APPLICATION

This application claims the priority benefit under 35 U.S.C. § 119(e) of U.S. Provisional Patent Application Ser. No. 62/725,610 entitled “Re-crosslinking Particle Gel for CO₂Conformance Control and CO₂Leakage Blocking,” filed Aug. 31, 2018, the entire disclosure of which is incorporated herein by reference

FIELD OF INVENTION

The present invention relates to the composition of particle gels for CO₂-EOR and CO₂storage. More particularly, the present invention generally relates to CO₂-resistant particle gels that can re-crosslink at subterranean conditions. These particle gels can be deployed to improve the conformance of CO₂flooding, CO₂huff-puff, or Water-Alternative-Gas (WAG). The applications also involve CO₂storage, such as the blocking of CO₂leakage and similar CO₂processing.

BACKGROUND

Carbon Dioxide-Enhanced Oil Recovery (CO₂-EOR), as a significant Carbon Capture and Storage (CCS) technology, contributes to reducing billions of tons of Greenhouse Gas (GHG) emissions in the U.S. market. Substantial CO₂-EOR projects have been established or are being launched across the U.S. market. For example, it has been reported in the Permian Basin of West Texas that approximately three kg of CO₂could be sequestrated and produce one kg of oil.

In spite of the notable industrial success, the incremental oil recovery of CO₂-EOR is still impeded. This deficiency of CO₂flooding is even more severe when CO₂bypassing encompasses the heterogeneity of the oil reservoir. Therefore, aimed at remedying the bypassing and heterogeneity problem, gel treatments are extensively studied and implemented for improvement of CO₂conformance.

Generally, the conventional gel systems include pristine preformed particle gels (“PPGs”), which have been found inadequate for remedying the reservoir fractures or conduits in virtue of “extrusion.” Moreover, the supercritical CO₂with intensive diffusibility is prone to breaking through the spacing within a gel pack and thereby deteriorates the plugging performance. Thus, additional improvements are still being sought in gel formulations.

SUMMARY

One or more embodiments of the present invention generally concern a swellable composition for controlling fluid flow. Generally, the swellable composition comprises a polymer matrix, a first crosslinker, and a second crosslinker. Furthermore, the polymer matrix comprises a first monomer having a re-crosslinking moiety, a second monomer having an acid resistance moiety, and a third monomer having a CO₂-phillic moiety.

One or more embodiments of the present invention generally concern a method of forming a swellable composition. Generally, the method comprises: (a) polymerizing a first monomer having a re-crosslinking moiety, a second monomer having an acid resistance moiety, and a third monomer having a CO₂-phillic moiety in the presence of a first crosslinker and a second crosslinker to form a polymer matrix; (b) drying the polymer matrix to form a dried polymer matrix; and (c) grinding the dried polymer matrix to form the swellable composition.

One or more embodiments of the present invention generally concern a method of altering or controlling a fluid present in a subterranean environment. Generally, the method comprises: (a) introducing a swellable composition into the subterranean environment so that the swellable composition contacts the fluid, wherein the swellable composition comprises a polymer matrix comprising a plurality of crosslinkable polymer chains, a first crosslinker, and a second crosslinker and wherein at least a portion of the second crosslinker is interspersed among the crosslinkable polymer chains of the polymer matrix; (b) allowing the second crosslinker to associate with the crosslinkable polymer chains upon exposure to the fluid to thereby form a swollen composition; and (c) at least partially controlling the flow of the fluid within the subterranean environment with the swollen composition. Additionally, the polymer matrix comprises a first monomer having a re-crosslinking moiety, a second monomer having an acid resistance moiety, and a third monomer having a CO₂-phillic moiety.

BRIEF DESCRIPTION OF THE FIGURES

Embodiments of the present invention are described herein with reference to the following drawing FIGURES, wherein:

<figref idref="DRAWINGS">FIG. 1</figref> depicts an exemplary CO₂-plugging method with the inventive CO₂-RPPG.

WRITTEN DESCRIPTION

The present invention generally relates to the composition of particle gels for CO₂-EOR and CO₂storage. More particularly, the present invention generally relates to CO₂-resistant particle gels that can re-crosslink at subterranean conditions. These particle gels can be deployed to improve the conformance of CO₂flooding, CO₂huff-puff, or Water-Alternative-Gas (WAG). The applications of the inventive particle gels may also involve CO₂storage, such as the blocking of CO₂leakage and similar CO₂processing.

In various embodiments, a new class of particle gels is provided that can re-crosslink at subterranean conditions and maintain stability in supercritical CO₂. The inventive particle gels disclosed herein may be referred to as CO₂-resistant re-crosslinked preformed particle gels (“CO₂-RPPG”). Generally, in one or more embodiments, the CO₂-RPPG comprises: (a) a polymer matrix, (b) a Crosslinker I, (c) a Crosslinker II, and (d) additives, wherein all of the aforementioned components are homogeneously distributed in the CO₂-RPPG when synthesized. In certain embodiments, the polymer matrix comprises three monomer moieties that may include: (i) a first monomer with a re-crosslinking moiety, (ii) a second monomer with an acid-resistance moiety, and (iii) a third monomer with a CO₂-philic moiety. These moieties may enhance and facilitate the crosslinking with crosslinker II, thereby preventing the particle gel from dehydrating and tuning the affinity of hydrophilicity and CO₂-phicility.

Furthermore, in various embodiments, the CO₂-RPPG may be used in a CO₂-plugging method as shown in <figref idref="DRAWINGS">FIG. 1</figref>. As shown in Step I of <figref idref="DRAWINGS">FIG. 1</figref>, injection wells and boreholes may be subjected to certain subterranean conditions that can exhibit high CO₂flow. Thus, as shown in Step II of <figref idref="DRAWINGS">FIG. 1</figref>, the CO₂-RPPG particles can be pumped into injection wells or boreholes at oilfields using brine or produced water as the carrier fluid. While subjected to these subterranean conditions, the CO₂-RPPG particles preformed by the polymer matrix and crosslinker I can be transported, along with the unreacted crosslinker II that is absorbed on the polymer matrix, into a target zone. After being placed into the target zone, the CO₂-RPPG particles may accumulate in the fractures or conduits, wherein the crosslinker II will gradually desorb from the precursor. Under the stimulus of the reservoir temperature, the active crosslinker II will cause all the particles of the CO₂-RPPG to stick together, and thereby generate an elastic bulk gel via crosslinking reactions (as shown in Step III of <figref idref="DRAWINGS">FIG. 1</figref>). This process, particularly the processing time, will be dependent on the reservoir temperature and the salinity of the carrier fluid, which can be artificially controlled by introducing reagents or additives. After re-crosslinking, a stable gel with good mechanical integrity will block the target zone or bypassing zone, and thereby divert the chased fluid (e.g., CO₂or water) to the unswept zone as shown in Step IV of <figref idref="DRAWINGS">FIG. 1</figref>. Consequently, the re-crosslinked gel may act as a robust CO₂-plugging agent and will not undergo dehydration or other chemical degradations induced by CO₂. Thus, the inventive CO₂-RPPGs may overcome the flaws of previous polymer gels, particularly the deficiencies associated with extrusion, dehydration, and mechanical vulnerability, and offer a superior alternative for CO₂conformance control and CO₂leakage blocking.

As noted above, the CO₂-RPPG generally comprises a polymer matrix, a Crosslinker I, a Crosslinker II, and additives, wherein all the components are homogeneously distributed in the CO₂-RPPG when synthesized. The synthesis of CO₂-RPPG is conducted using multiple chemical constituents. Generally, in various embodiments, the CO₂-RPPG may comprise at least 50, 60, 70, 80, 90, 95, or 99 weight percent of the polymer matrix. Furthermore, in various embodiments, the CO₂-RPPG may comprise at least 0.01, 0.02, 0.04, 0.06, 0.08, 0.1, 0.12, 0.14, or 0.16 and/or less than 20, 15, 10, 5, 4, 3, 2, or 1 weight percent of Crosslinker I, Crosslinker II, and/or the additives. Moreover, in various embodiments, the CO₂-RPPG may comprise a molar ratio of Crosslinker I to Crosslinker II in the range of 1:50 to 50:1, 40:1 to 1:40, 30:1 to 1:30, 20:1 to 1:20, or 10:1 to 1:10.

Generally, in various embodiments, the method for forming the CO₂-RPPG may comprise: (a) polymerizing the first monomer having a re-crosslinking moiety, the second monomer having an acid resistance moiety, the third monomer having a CO₂-phillic moiety in the presence of Crosslinker I and Crosslinker II to form the polymer matrix; (b) drying the polymer matrix to form a dried polymer matrix; and (c) grinding the dried polymer matrix to form a swellable composition, i.e., the CO₂-RPPG. In one or more embodiments, the polymerizing of step (a) occurs at a temperature of at least 20, 25, 30, 35, 40, 45, or 50° C. and/or less than 200, 150, 100, 75, or 60° C. Furthermore, in various embodiments, the polymerizing may comprise ultrasonication that occurs for at least 10, 20, or 30 minutes and/or less than 6, 5, 4, or 3 hours. Additionally, in various embodiments, the polymerizing may occur for at least 1, 2, 3, or 4 hours and/or less than 18, 15, 12, or 10 hours.

As discussed above, the polymer matrix of the CO₂-RPPG comprises three moieties: (i) a first monomer with a re-crosslinking moiety, (ii) a second monomer with an acid-resistance moiety and (iii) a third monomer with a CO₂-philic moiety.

Typically, the first monomer with the “re-crosslinking moiety” refers to the predominant portion or units in the polymer chain of the polymer matrix. Generally, this moiety is formulated and established by water-soluble monomers, which can be initiated by a free radical, while the monomers need to be crosslinkable by Crosslinker II at subterranean conditions, therein forming covalent, ionic, or coordination bonding.

In certain embodiments, the monomer comprising a re-crosslinking moiety is a monomer possessing an anionic charge at neutral pH (7.0). Representative anionic monomers may include sodium, potassium, and ammonium salts of acrylic acid, methacrylic acid, maleic acid, itaconic acid, 2-propenoic acid, 2-methyl-2-propenoic acid, other water-soluble carboxylic acids, or combinations thereof. In certain embodiments, the monomer comprising a re-crosslinking moiety comprises a water-soluble carboxylic acid.

In certain embodiments, the monomer comprising a re-crosslinking moiety can be nonionic, and possess no charge at a pH ranging from about 4 to about 10. Representative nonionic monomers can include, for example, N-isopropylacrylamide, N,N-diethylacrylamide, dimethylaminopropyl acrylamide, dimethylaminopropyl methacrylamide, acryloyl morpholine, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, dimethylaminoethylacrylate, dimethylaminoethyl methacrylate, maleic anhydride, N-vinyl pyrrolidone, vinyl acetate, N-vinyl formamide, or combinations thereof.

In certain embodiments, the monomers comprising a re-crosslinking moiety can be a combination of anionic and nonionic monomers. In one or more embodiments, the preferred monomer for a re-association of free gel particles moiety is an acrylamide or a derivative thereof.

In certain embodiments, the monomers comprising a re-crosslinking moiety can comprise sodium salts of acrylic acid, potassium salts of acrylic acid, ammonium salts of acrylic acid, methacrylic acid, maleic acid, itaconic acid, 2-propenoic acid, 2-methyl-2-propenoic acid, or combinations thereof.

In one or more embodiments, the polymer matrix may comprise at least 40, 45, 50, 55, 60, 65, 70, 75, or 80 and/or less than 99, 95, 90, or 85 molar percent of at least one monomer comprising a re-crosslinking moiety based on the total molar content of the first monomer with a re-crosslinking moiety, the second monomer with an acid-resistance moiety, and the third monomer with a CO₂-philic moiety.

Typically, the “acid-resistance moiety” denotes another portion or segments in the polymer matrix that exhibit insensitivities to a pH environment, particularly aqueous acidic conditions. This contrasts with conventional pristine particle gels and aqueous polymer gels, which commonly comprise sidegroups of carboxylate (—COO⁻) in their polymer chains and are sensitive to pH. For which the dissociation of carboxylic groups having a pKa value of 4.2 may account, the carboxylate (—COO⁻) sidegroups tend to associate with the protons that are produced by CO₂dissolving. These counterions, however, cause a reduction of electrostatic charging, thereby diminishing the repulsion between polymer chains. As a result, the conventional pristine particle gels and aqueous polymer gels will shrink and lose their original volume until an equilibrium of deswelling. However, due to the inventive formulation described herein, this phenomenon can be alleviated through the incorporation of an acid-resistant moiety into the CO₂-RPPG that is insensitive to the acidic environment, thereby preventing the collapse of chain spacing.

In certain embodiments, a monomer comprising an acid-resistance moiety is composed of a sulfonate (i.e., 2-acrylamido-2-methyl-1-propanesulfonic acid sodium salt (AMPS)), sulfate, or phosphate monomers which contain bulky group, and thereby facilitate chain spacing with steric hindrance. Moreover, these monomers may possess a low value of pKa, such as the sulfonate group that has a pKa value of 2.3. The representative monomers comprising an acid-resistant moiety may include a sulfonate, sulfate, or phosphate group; sodium or potassium vinylsulfonate and vinyl sulfate salts like sodium or potassium vinyl sulfates; phenyl vinyl sulfonate salts like sodium or potassium phenyl vinyl sulfate; and/or vinyl phosphate salts like sodium or potassium vinyl sulfate.

In certain embodiments, the monomer comprising an acid-resistance moiety comprises a monomer exhibiting a pka of less than 4, 3.5, 3, 2.9, 2.8, 2.7, 2.6, 2.5, or 2.4.

In certain embodiments, the monomer comprising an acid-resistance moiety may comprise water-soluble monomers that contain cationic pendant groups, such as diallyldimethylammonium chloride, (3-(methacryloylamino) propyl) trimethyl ammonium chloride, (2-(methacryloyloxy) ethyl) trimethyl ammonium chloride, vinylbenzyl trimethyl ammonium chloride, or combinations thereof. Additionally or alternatively, in various embodiments, the monomers with cationic pendant groups may include dimethylaminoethylacrylate methyl chloride quaternary salt, dimethylaminoethylacrylate benzyl chloride quaternary salt, dimethylaminoethylmethacrylate methyl chloride quaternary salt, or combinations thereof. In one or more embodiments, the monomer with an acid-resistance moiety may comprise 2-Acrylamido-2-methyl-1-propanesulfonic acid sodium salt (Na-AMPS).

In one or more embodiments, the polymer matrix may comprise at least 0.5, 1, 2, 3, or 4 and/or less than 50, 45, 40, 35, 30, 25, 20, 15, or 10 molar percent of at least one monomer comprising an acid-resistance moiety based on the total molar content of the first monomer with a re-crosslinking moiety, the second monomer with an acid-resistance moiety, and the third monomer with a CO₂-philic moiety.

As used herein, “CO₂-philic moiety” is defined as a portion or segments in the polymer matrix that comprises “CO₂philes.” As used herein, the term “CO₂phile” refers to a molecular entity that is attracted to CO₂molecules and has strong interactions with CO₂that are more thermodynamically favorable than the interactions with polar solvents.

The underlying mechanism in regard to gel performance in supercritical CO₂conditions may be strongly linked with the interactions between water, CO₂, and the polymeric surface. For a highly hydrophilic surface in CO₂, the water binding sites may overlap CO₂binding; thus, the CO₂adsorption capacity will be significantly reduced due to the severe competitive sorption. The binded water can be tightly adsorbed onto the pore wall of a gel, whereas CO₂tends to adsorb away from the wall toward the pore center, rather than forming a monolayer near the pore wall. As a result, CO₂molecules, favored by solubility and diffusivity, will transport through the immobilized water in hydrogel, therein forming passageways for permeation. To combat this phenomenon, the polymer matrices of the present invention comprise CO₂philes, which can modify the surface property of the polymer matrix and thereby improve the affinity to CO₂. Consequently, the CO₂molecule will adsorb onto the moiety or segment of the CO₂philes and be maintained, rather than transported via passageways. The free volume within the polymer matrix on that account may be reduced, and the flow hindrance for chased CO₂will be enhanced.

In certain embodiments, the CO₂-philic monomers may comprise vinyl benzoate, benzyl vinyl formate, ethyl vinyl ether, methyl vinyl ether, vinylidene fluoride, lactic acid or lactic acid cyclic dimmer, glycolic acid or glycolide, hexamethylcyclotrisiloxane, 1H,1H,2H,2H-perfluorooctyl methacrylate, or combinations thereof. In one or more embodiments, the preferred CO₂-philic monomer is vinyl acetate. Studies have shown that poly(vinyl acetate) (PVAc) has reasonable solubility in CO₂because of its amorphous structure, low melting point, and weak Lewis acid base interactions between the acetate group and CO₂.

In certain embodiments, the monomer comprising the CO₂-philic segment is synthesized by free-radical polymerization in aqueous solutions. In such embodiments, the CO₂-philic monomers (e.g., vinyl acetate) may be water-soluble and may co-polymerize with the re-crosslinkable monomers and acid-resistant monomers.

In various embodiments, the synthesis method of the CO₂-philic monomers is not limited and other polymerization routines such as ionic, ring-opening, or condensation polymerization can also be deployed. In some embodiments, the polymerization of the CO₂-philic monomers takes place within a different non-polar solvent, therein forming the configuration of a semi-inter penetrating network. In some embodiments, the CO₂-philes might be introduced by dispersion and may be incorporated in the form of a polymer, such as polyvinyl acetate.

In one or more embodiments, the polymer matrix may comprise at least 1, 2, 3, 4, 5, or 10 and/or less than 50, 45, 40, 35, 30, 25, 20, or 15 molar percent of at least one CO₂-philic monomer based on the total molar content of the first monomer with a re-crosslinking moiety, the second monomer with an acid-resistance moiety, and the third monomer with a CO₂-philic moiety.

As used herein, “Crosslinker I” is defined to include any reagents that can connect the polymer chains via crosslinkings, which take place simultaneously with the formation of polymer chains. In various embodiments, Crosslinker I is a divinyl monomer that can copolymerize with vinyl monomers and form crosslinking points during the propagation of polymers. At this point, the crosslinking denotes a chemical crosslinking, namely permanent, covalent bonding. Representative crosslinkers that may be used as Crosslinker 1 may include, for example, methylene bisacrylamide, diallylamine, triallylamine, divinyl sulfone, diethyleneglycol diallyl ether, or combinations thereof. In one or more embodiments, the preferred crosslinker is methylene bisacrylamide (MBA).

In certain embodiments, Crosslinker I comprises diacrylyl tertiary amide, diacrylylpiperazine, diallyltartardiamide, dihydroxyethylene-bis-acrylamide, and bis-acrylylcystamine, trimethylolpropane trimethacrylate, propyleneglycol triacrylate, tripropyleneglycol diacrylate, allyl methacrylate, triethyleneglycol dimethacrylate, tetrahydrofurfuryl methacrylate, trimethylolpropane triacrylate, or combinations thereof. In one or more embodiments, Crosslinker I may comprise a multifunctional crosslinker such as pentaerythritol triacrylate, 1,5 pentane diol dimethacrylate, pentaerythritol triallylether, or combinations thereof.

Crosslinker II may comprise any reagents that can react with the “re-associating moiety,” therein generating self-healing and discrete particle reassociations, to thus produce a bulk gel at subterranean conditions comprised of discrete polymer gel particles that associate to form a gel possessing bulk gel properties. More particularly, Crosslinker II is able to react with the sidegroups of the “re-crosslinking moiety” and thereby form coordination bonding, covalent bonding, ionic bonding, and/or physical tackifying. In other words, the polymer matrix may comprise a plurality of crosslinkable polymer chains and at least a portion of the Crosslinker II may be interspersed among the crosslinkable polymer chains. Consequently, the Crosslinker II may be capable of associating with the polymer chains upon exposure to a fluid capable of swelling the polymer matrix.

Crosslinker II can be either a single component or multiple components, which comprise multiple crosslinkers together as a combination.

In certain embodiments, Crosslinker II comprises a chelate comprising a multivalent metal ion (e.g., Al³⁺, Fe³⁺, cr³⁺, Ti⁴⁺, Sn⁴⁺, or Zr⁴⁺) and a ligand such as acetates, tartrates, malonates, propionates, benzoates, and/or citrates. The ligands may be organic ions complexed with a multivalent metal ion via coordination bonding, which can affect the kinetic rate of re-crosslinking. These crosslinkers can react with carboxyl groups or other reactive groups that are pendant on the “re-crosslinking moiety,” and thereby a bulk gel will be obtained in-situ. Representative Crosslinker II compounds can include, for example, Cr(III)-acetate, Cr(III)-propionate, Zr(IV)-acetate, Zr(IV)-lactate, or combinations thereof. In one or more embodiments, the preferred Crosslinker II is Zr(IV)-acetate.

In certain embodiments, Crosslinker II is polymeric component such as polyethyleneimine, poly-L-lysine, poly-ε-lysine, polyallylamine, polyvinylamine, or combinations thereof. These crosslinkers can connect neighbored amide groups via transamidation.

In various embodiments, the additives may comprise hydrophilic silica (e.g., silicon oxide) nanoparticles (“SNPs”) having an average size of at least 10, 15, 20, 30, 35, 40, 45, or 50 nm and/or less than 500, 400, 300, 200, 100, or 50 nm. The incorporation of SNPs, in one aspect, may contribute to an increase of interfacial area between the CO₂/water interface, therein forming a “3-phase contact line.” The adsorbed CO₂molecules, as a consequence, are prone to be stabilized. Moreover, the SNPs may split the large water clusters, which are attached to the polymer matrix, into smaller water-SNP hybrid clusters, therein leading to an enhancement of CO₂adsorption. Consequently, this may favor the resistance to CO₂. In one or more embodiments, the CO₂-RPPG may comprise at least 0.01, 0.02, 0.04, 0.06, 0.08, or 0.1 and/or less than 20, 15, 10, 5, 4, 3, 2, or 1 weight percent of one or more SNPs.

The SNPs, in another aspect, may reinforce the re-crosslinked hydrogel in regard to viscoelasticity and mechanical integrity. Generally, CO₂molecules are known plasticizers, which affect the chain mobility of the polymer and, thus, may decrease the glass transition temperature (Tg) of the polymers. However, the SNPs may function as anti-plasticizers and depress the shortscale cooperative motions, eventually favoring Tg. In virtue of the SNPs incorporation, more polymer chains may be confined within the vicinity of the SNPs, thereby inducing a reduction of the polymer chain's mobility. Hence, the additives may improve the hydrogel's modulus beyond that of a conventional pristine gel. Moreover, the resulting reinforcement of the gel pore-wall can alleviate the gel shrinkage that is induced by the capillary pressure occurred during water-CO₂exchange.

In various embodiments, the additives may comprise fibers, such as polyethylene fibers, PVA fibers, nylon fibers, or polypropylene fibers. The fibers may enhance the toughness of the resulting particle gels. In one or more embodiments, the fibers may have an average length of at least 1, 2, 3, 4, or 5 mm and/or less than 30, 25, 20, or 15 mm. Additionally or alternatively, in various embodiments, the fibers may comprise an average diameter of at least 1, 2, 5, or 8 microns and/or less than 100, 75, 50, or 40 microns.

Furthermore, in various embodiments, the CO₂-RPPG may comprise at least 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.08, or 0.1 and/or less than 20, 15, 10, 5, 4, 3, 2, or 1 weight percent of one or more fibers.

In various embodiments, the additives comprise both SNPs and an oxygen scavenger. Oxygen scavengers are reducing agents which can remove the dissolved oxygen from an aqueous solution through a gradual process of a redox reaction. In certain embodiments, the oxygen scavenger comprises dithionite salts (i.e., sodium dithionite), thiosulfate salts (i.e., sodium thiosulfate), sulfite salts (i.e., sodium sulfite), bisulfite salts (i.e., sodium bisulfite), metabisulfite salts, persulfate salts (e.g., ammonium persulfate), or combinations thereof. In one or more embodiments, the oxygen scavengers are bisulfite salts, such as ammonium bisulfite and sodium bisulfite. In other embodiments, the oxygen scavengers can comprise sodium thiosulfate, ammonium persulfate, sodium bisulfite, sodium metabisulfite, or combinations thereof.

Due to its unique formulation, the CO₂-RPPG may exhibit desirable shear modulus characteristics. In various embodiments, the CO₂-RPPG may exhibit a shear modulus of at least 80, 85, 90, 95, 100, 105, 110, 15, 120, 125, 150, 200, 250, 300, 350, or 400 Pa after being aged for 1 minute, 5 minutes, 1 hour, 12 hours, 1 day, 10 day, 20 days, or 30 days at 45° C. or 65° C.

Furthermore, the CO₂-RPPG may also exhibit desirable swelling properties due to its unique formulation. In various embodiments, the CO₂-RPPG may exhibit a swelling ratio of at least 5, 10, 15, 20, 25, 30, or 35 percent and/or less than 75, 60, 55, 50, or 45 percent after a time period of 2, 4, 6, 8, 10, 12, 15, 20, 25, 30, 35, or 40 hours at 23° C. or 73° C. in an aqueous solution comprising 0.5, 1, or 5 weight percent of NaCl at a pH of 1, 3, 5, or 7. The “swelling ratio” refers to the fractional increase in the weight of the particulate gel due to fluid absorption. The swelling ratio may be measured by the following formula:

<maths id="MATH-US-00001" num="00001"><math overflow="scroll"><mrow><mi>SR</mi><mo>=</mo><mrow><mfrac><msub><mi>V</mi><mrow><mi>particle</mi><mo>,</mo><mi>a</mi></mrow></msub><msub><mi>V</mi><mrow><mi>particle</mi><mo>,</mo><mi>b</mi></mrow></msub></mfrac><mo>=</mo><mrow><mfrac><mrow><msub><mi>V</mi><mrow><mi>total</mi><mo>,</mo><mi>a</mi></mrow></msub><mo>-</mo><msub><mi>V</mi><mrow><mi>water</mi><mo>,</mo><mi>a</mi></mrow></msub></mrow><mrow><msub><mi>V</mi><mrow><mi>total</mi><mo>,</mo><mi>b</mi></mrow></msub><mo>-</mo><msub><mi>V</mi><mrow><mi>water</mi><mo>,</mo><mi>b</mi></mrow></msub></mrow></mfrac><mo>.</mo></mrow></mrow></mrow></math></maths>&lt;br /&gt; In accordance with the above formula, dry particles may be placed into a graduated cylinder and brine (e.g. 1 wt % NaCl) with a certain volume (V_water,b) may be added. The total volume of the brine and particles (V_total,b) may then be obtained. The total volume can be read again as V_total,a, once the particle volume does not increase and is considered fully swollen. The remaining brine may then be screened out and measured again for volume, V_water,a.

In various embodiments, the CO₂-RPPG exhibits a storage modulus of at least 50, 100, 150, 200, or 250 Pa as measured at a frequency of 1 Hz and a stress of 1 Pa at ambient temperature (23° C.).

In various embodiments, the CO₂-RPPG may comprise an average particle size of at least 0.1, 0.2, 0.3, 0.4, or 0.5 mm and/or less than 10, 5, 4, 3, 2, 1, or 0.9 mm.

In various embodiments, the CO₂-RPPG may comprise an average particle size of 0.1 to 100 μm or as small as 10 nm, which can be obtained through grinding, ball milling or colloidal milling.

The CO₂-RPPG described herein may be used to improve the conformance of CO₂flooding, CO₂huff-puff, or Water-Alternative-Gas (WAG). The applications also involve CO₂storage, such as the blocking of CO₂leakage and similar CO₂processing. In various embodiments, the CO₂-RPPG may be used in a method of altering or controlling a fluid present in a subterranean environment, such as wells, pipelines, pipelines, or fractures. Generally, the method may involve introducing the CO₂-RPPG into a subterranean environment via a carrier fluid, such as brine or water, and allowing the CO₂-RPPG to contact a particular fluid, such as CO₂. In one or more embodiments, the carrier fluid can be selected from the group consisting of water, brine solvent (comprising NaCl, CaCl₂, and/or AlCl₃), and other fluids that cause the composition to swell.

Upon contacting the fluid, the Crosslinker II is capable of associating with the polymer chains of the polymer matrix upon exposure to the fluid. Consequently, the CO₂-RPPG may begin to swell upon contacting the fluid. This swelling indicates the association, crosslinking, and/or reassembly of the polymer matrix. In other words, the swelling may cause the CO₂-RPPG to associate, combined together, and form a bulk gel. In certain embodiments, the swelling may commence within 0.1 seconds to 300 seconds upon contacting the fluid.

In various embodiments, the CO₂-RPPG is in the form particles having an initial average particle size prior to contacting the fluid and a second average particle size after contacting the fluid and swelling. In such embodiments, the second average particle size can be at least about 5, 10, 15, 20, 25, 30, 35, or 40 times greater than that of the initial average particle size.

As used herein, the terms “a,” “an,” and “the” mean one or more.

As used herein, the term “and/or,” when used in a list of two or more items, means that any one of the listed items can be employed by itself or any combination of two or more of the listed items can be employed. For example, if a composition is described as containing components A, B, and/or C, the composition can contain A alone; B alone; C alone; A and B in combination; A and C in combination, B and C in combination; or A, B, and C in combination.

As used herein, the terms “comprising,” “comprises,” and “comprise” are open-ended transition terms used to transition from a subject recited before the term to one or more elements recited after the term, where the element or elements listed after the transition term are not necessarily the only elements that make up the subject.

As used herein, the terms “having,” “has,” and “have” have the same open-ended meaning as “comprising,” “comprises,” and “comprise” provided above.

As used herein, the terms “including,” “include,” and “included” have the same open-ended meaning as “comprising,” “comprises,” and “comprise” provided above.

The present description uses numerical ranges to quantify certain parameters relating to the invention. It should be understood that when numerical ranges are provided, such ranges are to be construed as providing literal support for claim limitations that only recite the lower value of the range as well as claim limitations that only recite the upper value of the range. For example, a disclosed numerical range of 10 to 100 provides literal support for a claim reciting “greater than 10” (with no upper bounds) and a claim reciting “less than 100” (with no lower bounds).

The preferred forms of the invention described above are to be used as illustration only, and should not be used in a limiting sense to interpret the scope of the present invention. Modifications to the exemplary embodiments, set forth above, could be readily made by those skilled in the art without departing from the spirit of the present invention.

This invention can be further illustrated by the following examples of embodiments thereof, although it will be understood that these examples are included merely for the purposes of illustration and are not intended to limit the scope of the invention unless otherwise specifically indicated.

Example 1

A representative CO₂-resistant re-crosslinking preformed particle gel was prepared using free radical polymerization in solution. The following abbreviations apply to all the Examples of the present application.

<tables id="TABLE-US-00001" num="00001"><table frame="none" colsep="0" rowsep="0"><tgroup align="left" colsep="0" rowsep="0" cols="2"><colspec colname="1" colwidth="42pt" align="left" /><colspec colname="2" colwidth="175pt" align="left" /><thead><row><entry namest="1" nameend="2" align="center" rowsep="1" /></row><row><entry>Abbreviation</entry><entry>Meaning</entry></row><row><entry namest="1" nameend="2" align="center" rowsep="1" /></row></thead><tbody valign="top"><row><entry>AMPS-Na</entry><entry>2-Acrylamido-2-methyl-1-propanesulfonic acid sodium salt</entry></row><row><entry>AM</entry><entry>Acrylamide</entry></row><row><entry>VAc</entry><entry>Vinyl acetate</entry></row><row><entry>Zr(Ac)₄</entry><entry>Zirconium acetate</entry></row><row><entry>MBAM</entry><entry>N,N′-Methylenebis(acrylamide)</entry></row><row><entry>APS</entry><entry>Ammonium persulfate</entry></row><row><entry>STS</entry><entry>Sodium thiosulfate</entry></row><row><entry namest="1" nameend="2" align="center" rowsep="1" /></row></tbody></tgroup></table></tables>

In a typical preparation, AMPS-Na (4.27 g, 19.42 mmol) and AM (22.5 g, 316.9 mmol) were added to the deionized water (100 mL). Under vigorous stirring, Zr(Ac)₄solution (5.86 mL) and VAc (5.38 mL, 58.14 mmol) were dropped, which was followed by an addition of MBAM (1.75 mg, 0.011 mmol). The silica nanoparticles (20 mg, 15-20 nm) were slowly added to the solution; the dispersion was then subjected to ultrasonication for 30 minutes. After bubbling with argon for 30 min, APS (80 mg, 0.35 mmol) was added; the dispersion was then subjected to heating in an oil-bath at 50° C. under vigorous stirring until the formation of the bulk gel. Polymerization was carried out for 6 hours, after which the bulk gel was dried and ground.

Example 2

A representative CO₂-resistant re-crosslinking preformed particle gel comprising SNPs was prepared using free radical polymerization in solution.

More particularly, AMPS-Na (4.27 g, 19.42 mmol), AM (22.5 g, 316.9 mmol), Zr(Ac)₄solution (5.86 mL, 16 wt % dissolved in acetate acid), VAc (5.38 mL, 58.14 mmol), MBAM (1.75 mg, 0.011 mmol), silica nanoparticles (20 mg, 15-20 nm), APS (80 mg, 0.35 mmol), and distilled water (100 mL) were combined under vigorous stirring and subjected to the polymerization conditions described in Example 1. The resulting bulk gel was dried and ground.

Example 3

A representative CO₂-resistant re-crosslinking preformed particle gel comprising a redox system was prepared using free radical polymerization in solution.

More particularly, AMPS-Na (4.27 g, 19.42 mmol), AM (22.5 g, 316.9 mmol), Zr(Ac)₄solution (5.86 mL, 16 wt % dissolved in acetate acid), VAc (5.38 mL, 58.14 mmol), MBAM (25 mg, 0.015 mmol), APS (80 mg, 0.35 mmol), STS (70 mg, 0.44 mmol), and 100 mL distilled water were combined under vigorous stirring and subjected to the polymerization conditions described in Example 1, except the polymerization occurred at 23° C. The resulting bulk gel was dried and ground.

Example 4

A representative CO₂-resistant re-crosslinking preformed particle gel comprising a fiber system was prepared using free radical polymerization in solution.

More particularly, AMPS-Na (4.27 g, 19.42 mmol), AM (22.5 g, 316.9 mmol), Zr(Ac)₄solution (5.86 mL, 16 wt % dissolved in acetate acid), VAc (5.38 mL, 58.14 mmol), MBAM (17.5 mg, 0.011 mmol), polypropylene fiber—ProCon M® (0.05 g), APS (80 mg, 0.35 mmol), and 100 mL distilled water were combined under vigorous stirring and subjected to the polymerization conditions described in Example 1. The resulting bulk gel was dried and ground.